Giuseppe Bilotta:
> I've recently found myself thinking about situations in which some
> kind of ‘feature detection’ for CSS browser support might be necessary
> (see later for details on such motivations). I've googled for relevant
> threads on this mailing list, but it seems to me that the main
> proposals that have been made on related topics have been focused on
> _browser_ detection.
You must have missed this while searching:
http://dev.w3.org/csswg/css3-conditional/